An electric motor is an electromagnetic device that converts electrical energy into mechanical energy based on the law of electromagnetic induction. It is widely used in various fields and is an indispensable prime motor for today's society, providing power source for a large number of electrical appliances or machines.
An electric toothbrush is a kind of motor-powered device. At present, the drive motor of electric toothbrush usually includes a mountain-shaped iron-core magnet yoke (also called E-shaped magnet yoke), permanent magnet (one piece or two pieces), and rotary output component, the permanent magnet drives the rotary output component to reciprocatively rotate under the action of a coil mounted on the mountain-shaped iron-core yoke. However, the magnetic flux of the middle support of the mountain-shaped iron-core yoke is large, the magnetic flux of the two ends of the magnetic yoke is small, and the force of the permanent magnet is small; and the housing and the rotary output component are required not to have magnetic conductive material to affect the magnetic circuit. Such kind of electric toothbrush require sufficient torque transmission, and must be guaranteed with spring resonance.